// truth.c -- 哪些值为真
#include<stdio.h>
int main(void)
{
    int n = 3;

    while (n)
        printf("%2d is true\n", n--);
    printf("%2d is false\n", n);

    n = -3;
    while (n)
        printf("%2d is ture\n", n++);
    printf("%2d is false\n", n);

    return 0;
}
//一般而言，所有的非零值都视为真，只有0被视为假。也就是说，只要测试条件的值为非零，就会执行while循环。